Determination of β-HCG using amperometric immunosensors based on a conducting immunocomposite

An amperometric immunosensor based on a rigid immunocomposite was built to measure human chorionic gonadotropin beta-subunit (beta-HCG). The immunocomposite is formed by a conducting graphite-methacrylate matrix containing the anti-beta-HCG antibody. The main advantage of this kind of immunosensors is their easy regeneration which can be achieved by a simple polishing of their surface. beta-HCG is determined with a sandwich assay using anti-beta-HCG conjugate labelled with horseradish peroxidase (HRP). The extent of the immunological interaction is quantified by the activity of the labelling enzyme: peroxidase is regenerated after the enzymatic reduction of H2O2 by hydroquinone which is used as a mediator in the solution. The reduction of hydroquinone is amperometrically monitored using a potential of -0.1 V. Each assay can be realised in less than 40 min. The upper limit corresponds to a beta-HCG concentration of 98.0 IU/I and the detection limit to 2.6 IU/I. (C)1999 Elsevier Science B.V. All rights reserved.